After being saturated with yellow solar energy in All-Star Superman, his strength was tested as exceeding the force of 200 quintillion tons (or 2x10^20 tons, in scientific notation, i.e., two hundred billion billion tons), enough to pull the Earth away from the sun.[volume & issue needed] As of The New 52 reboot, his strength now exceeds 5.972 sextillion metric tons.[volume & issue needed] Explanations include being adapted to the heavier gravity of Krypton, and his muscles using the power of the solar energy which fuels all his abilities. Superman's stamina has also been shown as limitless (whilst he remains in yellow sunlight).

So there we have a number on the upper limits of Supermans strength, I'll leave the math to someone more inclined to do it.

Superman in the new 52, still have a very unclear powerset, ive not read Superman issue 13 and 14 yet where he ''pumps'' earth for 5 days straight, so im trying to avoid that as a fact i use before ive read it.
In pre 52 his greatest feat was pulling earth together with Hal Jordan and another time when he pushed it together with Wonder Woman and Martian Manhunter...

When Superman liften 200 quintillion tons it was in All-Star Superman, a feat often used (by me also) but should be remembered as a non-cannon feat, all-star superman is a centered story and non-cannon.